On 26 September 2022, the NASA Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the secondary component of the binary asteroid (65803) Didymos (Daly et al. 2023). This experiment aimed to test the kinetic impactor deflection strategy. Due to the impact, the binary system’s angular momentum has changed, resulting in a significant change in the orbital period of Dimorphos. The orbital period was measured precisely by observing mutual events in the light curves of the system. An extensive ground-based photometric campaign resulted in a rich data set of light curves covering six apparitions between 2003 and 2023. Analysis of this data set and independent radar observations have shown that the orbital period has decreased by about 33 minutes (Thomas et al. 2023). The data set is described in detail in Pravec et al. (2022) and Moskovitz et al. (2024). We aimed to use these data to constrain a possible change in the rotation period of the primary as a consequence of the impact. Applying the binary asteroid lightcurve decomposition method (Pravec et al. 2022, 2024), we selected parts of the light curves taken at orbital phases outside the mutual events, subtracted the signal of the secondary component, and applied the light curve inversion method of Kaasalainen & Torppa (2001) and Kaasalainen et al. (2001) to reconstruct a convex shape model of Didymos and precisely determine its rotation period before and after the impact. We introduced another free parameter to the model – a change ∆ω of the rotation rate ω at the time of the DART impact. We assumed that before the impact, the model rotated with the angular frequency ω1, and then, after the impact but before the first post-impact observations, the frequency changed to ω2 = ω1 + ∆ω. The rotation phase φ of Didymos at some epoch t is then described as φ(t) = φ0 + (ω1 + ∆ω)(t − t0) , where φ0 is an initial rotation phase at the time t0 , ∆ω is zero for pre-impact data and nonzero for post-impact data. Both ω1 and ∆ω were parameters of the optimization that defined the pre-impact rotation period P1 = 2π/ω1 and the post-impact rotation period P2 = 2π/ω2 = 2π/(ω1 + ∆ω). We found the best-fit values 2.260 389 1 ± 0.000 000 2 h for the pre-impact period and 2.260 451 ± 0.000 008 h for the post-impact period. Their difference 0.22 ± 0.03 s is small yet significant, meaning that the rotation of Didymos has decelerated after the DART impact. A possible physical explanation might be the accretion of impact ejecta on Didymos, which affected its angular momentum. Although the impactor hit Dimorphos, some angular momentum may have been transferred to the primary component by accretion of ejecta (Richardson et al. 2022). However, numerical simulations need to show this as a realistic scenario.

References:

Daly, R. T., Ernst, C. M., Barnouin, O. S., et al. 2023, Nature, 616, 443

Kaasalainen, M., & Torppa, J. 2001, Icarus, 153, 24

Kaasalainen, M., Torppa, J., & Muinonen, K. 2001, Icarus, 153, 37

Moskovitz, N., Thomas, C., Pravec, P., et al. 2024, PSJ, 5, 35

Pravec, P., Meyer, A. J., Scheirich, P., et al. 2024, Icarus, 418, 116138

Pravec, P., Thomas, C. A., Rivkin, A. S., et al. 2022, PSJ, 3, 175

Richardson, D. C., Agrusa, H. F., Barbee, B., et al. 2022, PSJ, 3, 157

Thomas, C. A., Naidu, S. P., Scheirich, P., et al. 2023, Nature, 616, 448

How to cite: Durech, J. and Pravec, P.: The rotation period of asteroid (65803) Didymos before and after the DART impact, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-73, https://doi.org/10.5194/epsc-dps2025-73, 2025.

The Double Asteroid Redirection Test (DART) mission was a successful planetary defense demonstration of a kinetic impactor on Dimorphos, the satellite of binary near-Earth asteroid 63803 Didymos (Daly et al. 2023). The DART impact changed not only the orbit of the satellite Dimorphos about Didymos (Thomas et al. 2023), but also the orbit of the Didymos system about the Sun (Makadia et al. 2024). We report quantitative results of this heliocentric deflection, leading to a revised estimate of the momentum enhancement factor β as well as an estimate of the bulk density ρ of the target Dimorphos.

In the months following the DART impact, a series of stellar occultation campaigns led to a total of 18 observed occultations of the Didymos system from 2022-Oct-15 to 2023-Jan-22. These observations represent an exquisite astrometric data set, with reported errors of no more than a few milliarcseconds. Three of these observations were reported with <1 mas uncertainty, and the lowest reported uncertainty was 0.2 mas on 2023-Jan-22. With these measurements, the estimate of the Yarkovsky effect on Didymos became significantly more refined compared to the pre-impact estimates, but the effect of the DART deflection was not yet plainly discernible.

However, in May 2024–March 2025, observers detected four additional stellar occultations by Didymos. With this additional data, we estimate the change in velocity in the heliocentric along-track direction to be ∆V = -11.7 ± 1.3 μm/s. Given the known circumstances of the DART impact, this deflection implies β = 2.0 ± 0.3, which is consistent with, but somewhat lower than, previous reports (Cheng et al. 2023). A lower value of β implies a lower bulk density ρ of Dimorphos, and indeed, using the measured deflection of the Dimorphos orbit around Didymos (Naidu et al. 2024), we estimate ρ = 1.54 ± 0.22 g/cm³, indicating that Dimorphos is significantly under-dense with respect to Didymos.

How to cite: Chesley, S. R., Makadia, R., Herald, D., Farnocchia, D., Chabot, N. L., Naidu, S. P., Rivkin, A. S., Siakas, A., Souami, D., Tanga, P., Tsavdaridis, S., Tsiganis, K., Bouquillon, S., and Eggl, S.: First detection of an asteroid’s heliocentric deflection: The Didymos system after DART, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1331, https://doi.org/10.5194/epsc-dps2025-1331, 2025.

Introduction:  The NASA Double Asteroid Redirection Test (DART) mission tested planetary defense by performing a kinetic impact on Dimorphos, the smaller asteroid in the Didymos binary system, on September 26, 2022. The experiment aimed to validate kinetic impact as a method for asteroid deflection. The impact successfully shortened Dimorphos' orbital period by 33 ± 1 minutes [1], exceeding the mission's primary objective.

The momentum enhancement factor (β), measuring the momentum transferred via ejecta recoil, ranged between 2.2 and 4.9 [2], indicating that the momentum transfer was significantly greater than in a perfectly inelastic collision (β = 1). Without the ejecta effect, the orbital period reduction would have been approximately 7 minutes. This result aligns with pre-impact simulations.

Analysis of the ejecta distribution, modeled using data from the LICIACube spacecraft [3,4], revealed an ejecta cone with an elliptical base defined by half-angles of 69° and 51° [5]. This analysis highlights the critical role of ejecta in enhancing momentum transfer and confirms the effectiveness of kinetic impact for asteroid deflection.

Although the ejecta curtain can be approximated by a cone, the real physical structure is more complex than a cone, as evident from LUKE image data returned by LICIACube. As seen from Fig. 1, on both face-on and side-on views of the ejecta obtained during the flyby, it is clear that the ejecta curtain is a debris field  that is characterized by extended features originating from and around the impact location on Dimorphos. A critical understanding of the spatial distribution of these features in three dimensional space is required (a) to better understand how the momentum was distributed among escaping ejecta; (b) to constrain the ejection velocities of particles that are part of these structures; (3) to better estimate the mass of the ejecta, following radiative transfer calculations coupled with observed optical depths of features. As such, in this work we attempt to reconstruct the distribution of these features using LUKE data.

Figure 1: (a) A face-on view of the ejecta field during the approach phase of the flyby,  149 seconds after the impact, from a distance of 127.7 km from Dimorphos (b) an oblique view of the ejecta field during the final phase of the flyby, 189 seconds after the impact, from a distance of 144.3 km from Dimorphos.

Methods and Results: In order to accurately identify the extended features in both face-on and side-on/oblique images of the ejecta field, we first enhanced the images to highlight the details of the ejecta field using python scikit-image library [6]. Then we cropped the images to 400x400 px frames, centred on Dimorphos. These were then compiled to make short video clips thus enabling us to track the features in consecutive images.

Figure 2: Identified 12 features in both front, side and oblique viewing geometries.

Upon successful identification of 12 features (Fig. 2) , using the 3D animation software Blender (version 3.5), we trace out delimiters around each of the features in both face-on and side-on images. Next, we populate homogenous and evenly spaced cubic particles around Dimorphos inside a cube of 2km a side, and capture the particles that are inside the aforementioned delimiters of a given feature (Fig. 3) in face-on image (we use cubic particles of 50m per a side, comparable to the spatial resolutions of several LUKE pixels during the flyby). Next we switch to the simulation of the side-on view/ oblique view of the ejecta and populate the restricted particles from the previous step. Then, using the delimiters of the same feature in this different observing geometry we further restrict the volume in space that corresponds to the feature in question. Similarly we iterate over other features and obtain the 3D orientations and span of all the identified features. Transformations among different LUKE camera orientations are performed using NAIF/SPICE[7] package offered by Python3 package spiceypy[8].  

Figure 3: An example of an identified feature and how its delimitation is used to constrain the particles that are along the line of sight of this feature, in this case of a face-on image, superposed over a simulation of the observation. The origin of the coordinate system is at the centre of Dimorphos.

In Fig. 4, can be visualized the simulation of the ejecta field observation along with a LUKE image.

Figure 4. Left – LUKE image featuring the ejecta field observed with an oblique geometry as LICIACube was leaving the Didymos system following the closest approach. Right – Simulation of the ejecta field at the same time and geometry using the ejecta features retrieved using our method.

We then used images with longer exposure times to estimate the extends of ejecta features and thereby derive lower limits for ejecta velocities. Out of the features we used for this estimation, we found velocity ranges in the range of 30-70 m/s. We will present the final results and discuss the implications at the conference.

Acknowledgments: The LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP F84I190012600).

References:

• [1] Thomas et al. (2023), Nature, 616, 448
• [2] Cheng et al. (2023), Nature, 616, 457
• [3] Dotto et al., (2011), PSJ, 199, 105185
• [4] Impresario et al., (2025), Acta Astronautica, 231, 223-234
• [5] Deshapriya et al. (2023), PSJ, 4:231
• [6] van der Walt et al. (2014), PeerJ 2:e453
• [7] Acton, C. H. (1996), P&SS, 44, 65
• [8] Annex, A., Pearson, B., Seignovert, B., et al. (2020), JOSS, 5, 2050

How to cite: Deshapriya, J. D. P., Hasselmann, P. H., and Dotto, E. and the LICIACube team: Reconstruction of ejecta distribution of DART spacecraft impact on asteroid Dimorphos using data from LICIACube/LUKE, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-698, https://doi.org/10.5194/epsc-dps2025-698, 2025.

DART (Double Asteroid Redirection Test) was the first mission dedicated to demonstrating an asteroid deflection technique by altering an asteroid’s trajectory through kinetic impact. On September 26, 2022, the DART spacecraft impacted Dimorphos, the secondary component of the Didymos binary asteroid system, generating a substantial ejecta plume. This ejecta affected the momentum transfer and led to a larger-than-expected change in Dimorphos' orbital period, exceeding 33 minutes [1]. The Italian Space Agency’s LICIACube, deployed as a follow-up observer, captured this event with its LEIA and LUKE cameras.

A key parameter of the DART mission is the estimation of the momentum enhancement factor (beta), which quantifies the momentum transfer resulting from the impact. Accurate estimation of beta requires characterization of the DART ejecta and an estimate of the total ejecta mass. To characterize the physical properties of the ejecta and their temporal variations as observed in post-impact LICIACube images,  we have simulated the ejecta plume using  the 3D radiative transfer code Hyperion (https://www.hyperion-rt.org/). Hyperion employs the Monte Carlo technique to simulate photon propagation through a scattering medium, accounting for multiple scattering effects.

A detailed analysis of the ejecta requires consideration of the three-dimensional geometry of the impact event, including the relative positions of Didymos, Dimorphos, LICIACube, and the Sun. The geometric parameters of the ejecta plume were derived for the LUKE image taken 175 seconds post-impact using DART SPICE kernels [2]. In our modeling, we use the recently calibrated images reported in [3]. Dust modeling parameters include the single-scattering albedo, brightness and polarization phase functions, and the cross-sectional properties of dust particles, defined by their size and number density. These were modeled assuming a typical S-type asteroid composition for Dimorphos. We adopted a single-scattering albedo of 0.55 and used brightness and polarization phase functions based on laboratory measurements of various (up to millimeter-sized) silicate grains [4, 5]. The ejecta plume was modeled as a hollow cone, characterized by impact location, tilt, and opening angle. As a starting point for the dust number density distribution within the cone, we used the distribution derived from the mass distribution in numerical impact simulations [6]

Our current best-fit model reproduces the LUKE image taken 175 seconds after impact, with a focus on the near-surface region of Dimorphos. Assuming an azimuthally uniform number density, we successfully simulated the structure of the ejecta plume, including the dark band adjacent to Dimorphos. This feature is likely a shadow cast by one of the optically thick cone walls onto the other. To address inhomogeneity in the ejecta, we used azimuthally averaged brightness values at specific distances from the asteroid. Comparison between observed and modeled brightness profiles provides constraints on the dust particle size distribution and number density, as well as their spatial variation. We show that the observed and modeled brightness profiles follow similar trends, including the dark band near the surface. Fitting the observed radiance values across the plume allows us to refine the number density estimates and derive the mass distribution within the plume.

The developed numerical approach and its results can serve as a template for characterizing dust in active asteroids, providing their dust size distribution, number density, and mass loss.

[1] Cheng, A.F., et al., 2023, Nature, 616(7957), 457-460.

[2] Nair, H. and Costa Sitja, M., 2023. DART SPICE Kernel Archive Bundle. NASA PDS, NAIF p.104.

[3] Farnham, T.L., 2025, LICIACube Calibrated and Merged LUKE Images V1.0. NASA Planetary Data System, https://10.26007/5vhp-pe80

[4] Munoz, O., et al., 2020, ApJ Suppl. Series, 247,19.

[5] Lolachi, R., et al., 2023, PSJ, 4, 24.

[6] Raducan, S. D., et al., 2024, Nature Astronomy, 8(4), 445 -455.

How to cite: Kim, Y., Kolokolova, L., Farnham, T., and Raducan, S.: Characterization of DART Ejecta Using 3D Radiative Transfer Modeling and LICIACube Observations, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-764, https://doi.org/10.5194/epsc-dps2025-764, 2025.

The aftermath of one of the most known Planetary Defence missions, is still intensely studied. The DART space mission to test kinetic impact deflection, successfully impacted Dimorphos, the moon of the binary asteroid Didymos and it’s primarily objective was achieved by altering the orbital trajectory of the asteroid. The collision ejected sufficient mass to transform Dimorphos into the first made-made active asteroid (Chabot L. N. et al., 2024).

Using the TRAPPIST twins located in Morocco and Chile (Jehin E. et al., 2011), respectively, we observed the evolution of the ejecta tail formed after the DART impact on Dimorphos. We obtained photometric data for several months before and after the impact, and the measurements and analysis obtained focused on the tail’s morphology, mass determination, color indices, ejecta dynamics and composition.

We present a preliminary mass estimate of the ejecta tail derived from the photometric measurements using the COMETails pipeline (Moreno F., 2025), as we modeled the tail’s formation and evolution, constraining the ejecta particle velocity, size distribution and the total mass of the dust. We also present the characteristics and evolution of the additional tails that were present shortly after the impact and that were visible for a shorter period of time.

Considering the most important aspect of the impact, the modified trajectory of Dimorphos, we also determined from TRAPPIST lightcurves the orbital change in the rotational period by analysing the mutual events of the system the few weeks before and after the impact. 

These results complement the previously published ground-based observations and, when analyzed together with impact and dynamics models, provide better constraints on impact-driven ejecta dynamics and contribute to a broader understanding of asteroid deflection techniques.

How to cite: Petrescu, E., Jehin, E., Karatekin, O., and Ferrais, M.: TRAPPIST results of the Didymos system after the DART mission, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1376, https://doi.org/10.5194/epsc-dps2025-1376, 2025.

The Hera mission was launched on October 7, 2024 and performed succefully a flyby of Mars on March 12, 2025, which placed the spacecraft on its trajectory to the binary asteroid Didymos. Hera will approach Didymos in October 2026 and start its close proximity operations in December 2026 for a nominal mission duration of 6 months. It will be the first mission to explore an asteroid using an architecture that includes a motherspacecraft and two CubeSats, Milani and Juventas, that will be deployed at the asteroid for close proximity operations, mineralogical measurements, dust detection and analysis, the first radar probing of the internal structure of an asteroid and landing. Once landed, the Juventas Cubesat will use a gravimeter to perform gravity field measurements. Radio Science and inter-satellite links will also be used for this purpose.

During the flyby of Mars, Hera also took images of the face opposite to Mars of the smaller moon of Mars, Deimos, using the asteroid framing cameras, the hyperspectral imager (Hyperscout-H) and the JAXA-contributed thermal infrared imager (TIRI) . 

We will present the main operations achieved so far, the status of the mission and the objectives at Didymos, which will contribute to the first asteroid deflection test with the NASA DART mission, and the first full characterization of a binary asteroid, including its internal properties. 

How to cite: Michel, P., Küppers, M., Fitzsimmons, A., Green, S., Lazzarin, M., Ulamec, S., Abell, P., Sugita, S., and Carnelli, I.: The ESA Hera mission on its way to the binary asteroid Didymos: characterization of the asteroid and full documentation of the NASA DART impact, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-119, https://doi.org/10.5194/epsc-dps2025-119, 2025.

The ESA Hera Planetary Defence mission was sucessfully launched from Cape Cañaveral in October 7, 2024, with the goal of studying in detail the near-Earth binary asteroid system (65803) Didymos-Dimorphos[1]. The smaller of the two objects, asteroid Dimorphos, was impacted by the NASA DART spacecraft in September 26, 2022, as part of the first test of the kinetic impactor deflection technology. DART impact changed the orbital period of Dimorphos around Didymos, measured to be around 12 hours, in a total of 33.24 ± 0.03 minutes [2], generating a huge cloud of dust and debris observable from the Earth, and that lasted for almost a year [3]. After a successful comissioning phase, were the Hera spacecraft tested most of its instruments and imaged the Earth-Moon system, the mission entered the cruise phase. This phase included the Mars swing-by in mid March, 2025, when images of the surface of the red planet were acquired for calibration purposes, in addition to one “extra” scientific target: the anti-Mars side of Deimos. The spacecraft is now traveling to its final destination, the Didymos-Dimorphos system where it is expected to arrive in late 2026, starting the asteroid phase. This includes different mission phases in which the spacecraf will progressively reduce its distance to the asteroid system, getting as close as ~1 km to the surface of Dimorphos at the final stage, in June-July 2027.

The Didymos-Dimorphos system has been extensively observed in the visible and the near-infrared using ground-based telescopes [4,5,6] and also the JWST[7]. Acquired data indicate that the unresolved system can be taxonomically classified as an S-type, i.e., it is relatively bright (average geometric albedo around 15%) and is dominated by mafic silicates, mostly pyroxene and olivine. These minerals show two very characterisic absorption bands in the visible and near-infrared wavelength region (0.5-2.5 µm), centred at 1 and 2 µm, that, together with the spectral slope, can be used to infer compositional information on the surface of the asteroids. Also, effects of space weathering in such surfaces have been broadly studied, with a decrease in albedo and band depth, and a reddening in the slope observed with increasing exposition [8].

One of the instruments onboard the Hera spacecraft is HyperScout-H (HS-H hereafter). This is a hyperspectral imager developed by cosine¹ with a large field of view (15° x 8°) and a CMOS detector exhibiting 2048 x 1088 pixels. The sensor incorporates a filter array consisting of on-chip, pixelated Fabry-Pérot interference filters, sampling a total of 25 bands in a configuration of 5 x 5 detector pixels and covering the 650 to 960 nm wavelength range. This instrumental setup allows to obtain both spectral and spatial information in one shot, the latter depending on the extent to which the original resolution can be restorted by demosaicking tecniques.

How to cite: de Leon, J., Popescu, M., Prodan, G., Küppers, M., Grieger, B., Kovacs, G., Nagy, B., Kohout, T., Lazzarin, M., Vincent, J.-B., and Licandro, J.: Observations of the Didymos-Dimorphos binary asteroid system with HyperScout-H instrument onboard the ESA Hera mission: what to expect at the arrival, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-815, https://doi.org/10.5194/epsc-dps2025-815, 2025.

Introduction: TIRI is an uncooled bolometer based thermal infrared imager with a filter wheel, developed by the Japan Aerospace Exploration Agency (JAXA) for the Hera mission led by the European Space Agency (ESA). Hera is a Planetary Defense mission to rendezvous with and explore the asteroid binary 65803 Didymos and its moon Dimorphos whose orbit around Didymos was deflected due to the kinetic impact by the Double Asteroid Redirection Test (DART) mission on 26 September 2022. The Hera spacecraft was launched on 7 October 2024, changed its trajectory to the asteroid binary by the gravity assist of Mars during the Mars Swing By on 12 March 2025, and will arrive at the targets in December 2026 and start the observations there. The current status and the future operation plan for TIRI will be briefly described.

In-Flight Performance of TIRI: We confirmed the instrument has been healthy after launch by having performed the initial function checks after launch, taken many sets of the Earth-Moon system images at various distances from the Earth, and a couple of Dark Sky imaging campaigns. The radiative calibration of TIRI has been carried out using Earth thermal images, even though their diameters are smaller than 0.5°, compared with those of the weather satellites as well as Moon thermal images compared with a thermal modeling of the Moon. The geometrical corrections of TIRI, i.e. alignments and distortions, has been conducted using the SPICE kernel provided by ESA Hera team. The calibrated TIRI data is almost ready now.

TIRI Observations during Mars Swing By: We have observed Mars and its moons Deimos and Phobos mainly for the purposes of TIRI calibration. Mars was a point source on 1 March but it was getting larger to cover the entire FOV of TIRI on 12 March, so that it is useful for the calibration of the size of source effect by comparing with the Mars thermal model and the observed data by EMIRS on UAE Mars Mission Hope and THEMIS on NASA Mars Odyssey. The comparison with the multiband filters will be also planned. Deimos has been imaged with all the bands of TIRI, so that the thermophysical properties and the constituent materials of its surface will be constrained. Crescent Phobos images of less than 10 pixel diameter have been taken during the Mars Swing By operation, which will be used for the relation of phase angle dependency of thermal emission to the surface geologic features.

Future Observation Plan for TIRI: We started to plan the asteroid phase operations. For TIRI, one-rotation thermal imaging (60-120 images in one rotation) of Didymos and Dimorphos as well as 8-band imaging (6-12 times in one rotation) will be planned from East, West, North, and South directions to investigate thermophysical properties, and during the Early Characterization Phase (ECP) and the Payload Deployment Phase (PDP) at 20-30 km distances for the first 8-9 weeks. Additionally, imaging at a higher frequency will be planned for tracing the shadows of Dimorphos is on Dimorphos and Dimorphos is in the shadow of Didymos. Similar observations but adding the imaging from the Noon direction will be planned during the Detailed Characterization Phase at 8-20 km distances for the next 4 weeks. After this phase, the spacecraft will perform flyby the asteroid binary at 4 km distances. During the close flyby, one-rotation thermal imaging of Didymos at a closest distance and at 20 km distances at high solar phase angles, as well as imaging of Dimorphos focusing on the DART impact area at higher spatial resolution at 1 m/pixel will be planned, during the Close-up Operation Phase (COP) for the next 6 weeks. Finally, much closer flyby observations to take images at higher spatial resolution will be planned at < 2 km distances during the Experimental Phase (EXP) for the last 6 weeks. Further detailed observation plan of TIRI will be reconsidered at a later stage of the mission.

How to cite: Okada, T., Tanaka, S., Sakatani, N., Shimaki, Y., Arai, T., Senshu, H., Demura, H., Sekiguchi, T., Kouyama, T., Kanamaru, M., Ishizaki, T., Vilardell Belles, R., Furukawa, S., Karatekin, O., Blommaert, J., Ruiz Lozano, L., Henry, G., Leon Tavares, J., Ritter, B., and Temel, O. and the Hera TIRI Team: In-Flight Performance of Hera TIRI and its Future Operation Plan, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1166, https://doi.org/10.5194/epsc-dps2025-1166, 2025.

ASPECT is a flexible hyperspectral imager based on tunable Fabry-Perót interference filter (Näsilä and Kohout 2020). It consists of three independent Vis-NIR imaging channels, one single-point SWIR spectrometer, and a dedicated data processing unit (DPU) based on Xiphos Q7 (Table 1). ASPECT is the prime payload of Milani CubeSat carried by ESA Hera mission (Michel et al. 2022, Kohout et al. 2018) to binary asteroid Didymos-Dimorphos and is also considered for missions to asteroid Apophis.

Tests of ASPECT performance to resolve spectral features of chondritic materials spectra were done with Bjurböle L/LL4 meteorite. 1-µm silicate band is well resolved (Fig. 1) and SNR around 100 in Vis channel and 40 in NIRs channels can be achieved.

ASPECT will conduct global hyperspectral mapping of the target asteroids with a resolution of 1 m/px from 5 km. The spectral domain contains key information on surface composition and maturity. Combined with high spatial resolution lateral variations in surface properties can be mapped.

Table 1.

Fig. 1. Comparison of Bjurböle meteorite measurements with ASPECT (green, red) against the reference laboratory spectrometer (blue). The 1-µm silicate band is well resolved.

References:

Michel et al. 2022 DOI 10.3847/PSJ/ac6f52

Näsilä, Kohout 2020 DOI 10.1109/AERO47225.2020.9172437

Kohout et al. 2018 DOI 10.1016/j.asr.2017.07.036

How to cite: Kohout, T., Korda, D., Penttilä, A., Ranttila, S., Syrjänen, S., Pitkänen, V., and Palamakumbure, L.: Detection of composition, space weathering, and local resurfacing using ASPECT hyperspectral imager of ESA Hera / Milani mission, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1353, https://doi.org/10.5194/epsc-dps2025-1353, 2025.

The ESA Hera mission, successfully launched on 7 October 2024, is a Planetary Defence Mission in combination with NASA DART (Double Asteroid Redirection Test) Mission, a mission kinetic impactor test, that impacted Dimorphos, i.e., the smallest body of the Didymos binary system, in September 2022.

Hera aims at demonstrating new technologies, from autonomous navigation around an asteroid to low gravity proximity operations, and at investigating the Didymos binary system, including the assessment of its internal properties and its geophysics characterization [1]. In addition to the remote sensing suite of instruments, Hera also carries two CubeSats, Juventas and Milani [2], that will be deployed in the vicinity of the asteroid system, providing unique scientific measurements.

One of the payload onboard Milani CubeSat is VISTA (Volatile In-Situ Thermogravimeter Analyser), a QCM-based device (Quartz Crystal Microbalance), whose scientific goals are the characterization of the dust environment of Didymos binary system, the detection of dust particle smaller than 5 µm, volatiles and light organics and the assessment of onboard contamination during the mission. VISTA is composed of three different units: two quartz crystals mounted in a sandwich-like configuration; the Proximity Electronics and the Thermal Control System (TCS), i.e., the customized resistors and a Thermo-Electric Cooler (TEC) to facilitate the particles deposition.

Thanks to its customized subsystem design, VISTA is capable of monitoring deposition and desorption/sublimation processes in space and molecular contamination, and performing Thermo-Gravimetric Analysis (TGA) on the collected materials [4], [5].

VISTA Flight Model is shown in Figure 1.

Figure 1. VISTA Flight Model mounted in its transport container.

VISTA was developed by an Italian Consortium led by INAF-IAPS (Istituto Nazionale di AstroFisica-Istituto di Astrofisica e Planetologia Spaziali), in collaboration with CNR-IIA (Consiglio Nazionale delle Ricerche-Istituto sull’Inquinamento Atmosferico) and Politecnico di Milano-MetroSpace Lab. The instrument is based on the heritage of different ITT-Emits ESA Projects: CAM (Contamination Assessment Microbalance), developed for “Evaluation of an in-situ Molecular Contamination Sensor for space use” (2014-2016); CAMLAB (Contamination Assessment Microbalance for LABoratory) developed for “Development of a European Quartz Crystal Microbalance” (2017-2019), and CAMLAB 2.0 developed for “European QCM: Bridging from Technical Development to Commercialisation” (2021-2024).

VISTA payload, including 1 Engineering Qualification Model (EQM), 1 Flight Model (FM) and 1 Flight Spare (FS) was developed in less than three years starting from late 2020. During this time, the instrument was also tested (Qualification and Acceptance tests on VISTA EQM, FM and FS were performed at INAF-IAPS and Politecnico di Milano-MetroSpace Lab) in vacuum and cryogenic environment to monitor absorption/desorption and deposition/sublimation processes to monitor the mass particles deposition lower than 5µm and sub-µm particles [5,6].

Figure 2 shows an example of a deposition test: an organic compund is heated in the Field Of View (FOV) of the instrument. The plot on the left shows the increase of frequency (black curve) with the heating steps of the organic component. In the second plot, a TGA test is shown: the crystals are heated by the built-in heaters after the depositon test to regenerate the crystals and characterize the organic compund by evaluating the sublimation temperature and the entalpy of sublimation.

Figure 2. Deposition test and TGA in vacuum.

Following the deployment of Milani in early 2027, the experimental phase will begin. VISTA will operate in Accumulation Mode (i.e., passive accumulation of dust and volatiles) and Active Modes (i.e., by using TEC and/or integrated µ-heaters) to promote the volatiles/compounds deposition and to characterize their desorption through Thermogravimetric Analysis, respectively. After the first in-orbit commissioning, VISTA behaviour was reported nominal.

References:

[1] Michel P. et al., “The ESA Hera Mission: detailed characterization of the DART impact outcome and of the Binary Asteroid (65803)”, Didymos” 2022 Planetary Science Journal 3:160

[2] Cardi M. et al., “The Hera Milani Mission”, Space Science Review 2024 (under review)

[3] Palomba E. et al., “VISTA: dust and volatile sensor for the ESA Hera mission”, Space Science Review 2024 (under review)

[4] Dirri F. 2016, AMT, 9, 655-668

[5] Dirri F. 2018, IEEE Xplore Digital Library, pp. 150-154, doi: 10.1109/MetroAeroSpace.2018, 8453532

[6] Zampetti, E. 2023, Sensors 2023, 23, 5682

How to cite: Palomba, E., Dirri, F., Gisellu, C., Longobardo, A., Nardi, E., Zampetti, E., Saccabarozzi, D., Corti, M. G., Saggin, B., and Cardi, M.: VISTA, a dust sensor for the ESA Hera mission, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1719, https://doi.org/10.5194/epsc-dps2025-1719, 2025.

Asteroid 2024 YR4 is a Near-Earth Asteroid expected to pass through the Earth-Moon system in December 2032. While the risk of an Earth impact has been ruled out, the asteroid is still expected to pass close to the Moon, and even a lunar collision cannot be excluded. This early prediction offers a rare opportunity for a low-cost mission to investigate a small asteroid. We have recently begun exploring the feasibility of a kinetic impact mission targeting 2024 YR4. We propose sending a small spacecraft as a rideshare payload on a future lunar mission, and to keep it in lunar orbit until the asteroid approaches in 2032. The spacecraft would separate into two components, one designed to collide with the asteroid and the other equipped to observe the encounter from a safe distance. We focus on estimating the expected changes in YR4’s heliocentric orbit and spin state following the impact, and on evaluating whether these changes could be detected through follow-up observations. The mission would provide a valuable chance to observe a fast-spinning small asteroid at close range, along with 1998 KY26, a target of the Hayabusa2♯ mission. It would also contribute useful data for developing and validating kinetic impact techniques in the context of planetary defence.

How to cite: JeongAhn, Y., Kim, P., Kim, M., Lee, H.-J., Song, Y., Moon, H.-K., Park, S.-J., and Park, S.-Y.: Exploring a Kinetic Impact Mission to Asteroid 2024 YR4, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1358, https://doi.org/10.5194/epsc-dps2025-1358, 2025.

Given present-day asteroid discovery capabilities, near-Earth asteroids (NEAs) are routinely discovered. 3,123 NEAs were discovered in 2024 alone¹. Furthermore, new telescopes such as the Vera C. Rubin Observatory and the planned NEO Surveyor spacecraft are set to increase NEA discovery rates in the coming years (Mainzer et al., 2011; Schwamb et al., 2023). Once the orbit of a new object is determined, we must assess its Earth impact hazard. If a large enough asteroid is found to be on a collision course with the Earth, a deflection mission must be developed to mitigate the asteroid’s impact hazard. Thanks to NASA’s Double Asteroid Redirection Test (DART) mission, a Kinetic Impact (KI) is a demonstrated method of changing an asteroid’s trajectory (Chabot et al., 2024).

Most asteroids that pose a significant impact hazard usually allow multiple impacts with the Earth over the span of decades. For example, Chesley et al. (2014) found that the orbit of asteroid (101955) Bennu allowed for more than 200 potential Earth impacts between 2167 and 2200. As it stands on 16 April 2025, more than 80% (29 out of 36) asteroids that have a Palermo asteroid impact hazard scale rating of -4 or greater admit more than one impact given their orbital uncertainties². The fact that small variations in an asteroid’s orbit can cause future impacts has consequences for KI mission planning. Uncontrolled deflection can, for instance, unlock gravitational keyholes. Doing so can unlock a gravitational keyhole (Chodas, 1999). If pushed into a keyhole, an asteroid would return on an impacting trajectory. This means another deflection mission on possibly much shorter timescales could become necessary.

In order to avoid such repetitive doomsday scenarios right off the bat, we should strive to design the initial KI deflection mission such that it does not trigger a keyhole (Chesley and Farnocchia, 2014; Eggl et al., 2018). In this work, we have developed a method that can aid KI mission decision-makers during the initial design process. We use realistic flyby mission trajectories that are already publicly available³ to obtain the KI velocity and mass at impact. We then combine this information with details of an impacting asteroid’s orbit, such as the keyhole locations and physical properties (like shape, spin state, and mass) and model hundreds of millions of KI mission outcomes. For each mission, we factor in realistic values of the momentum enhancement parameter as measured from the DART mission (Makadia et al., 2025).

The change in the target asteroid’s velocity resulting from the KI mission is then mapped to the scattering encounter to assess whether a particular mission realization has the potential to trigger a keyhole. The impact probability of the asteroid following each simulated KI mission is then computed using the impact probabilities of each reachable keyhole. This information is convolved with realistic targeting uncertainties for a KI spacecraft. Finally, this process is repeated over one rotation phase of the asteroid to allow for additional control over the exact time of KI deflection.

As a result of this process, we can map the 2014 keyholes of Bennu onto the surface of a target asteroid. Generating these impact probability maps allows KI mission designers to select the optimal site on the asteroid such that the post-deflection impact probability of the asteroid is minimized. Figure 1 shows a representative keyhole map on the surface of Bennu. The crosshair shows the optimal deflection site that minimizes the post-deflection impact probability of Bennu. By creating these maps, we can push asteroids away from the Earth such that they do not return on an impacting trajectory in the foreseeable future. We believe that this work is the next step in designing comprehensive KI deflection missions to ensure humanity’s continued safety from NEAs.

Figure 1: Example post-deflection asteroid impact probability map on the surface of (101955) Bennu. The crosshair corresponds to the location on the surface that minimizes the asteroid impact hazard after deflection. These results assumed a 25-meter targeting uncertainty for the KI spacecraft. As a result, deflection sites that allowed for a KI miss are not considered and form a gray boundary around the targetable region of the asteroid.

¹https://cneos.jpl.nasa.gov/stats/totals.html
²https://cneos.jpl.nasa.gov/sentry/
³https://ssd.jpl.nasa.gov/tools/mdesign.html#/interactive

References
A. Mainzer et al. NEOWISE OBSERVATIONS OF NEAR-EARTH OBJECTS: PRELIMINARY RESULTS. The Astrophysical Journal, 743(2):156, December 2011. doi: 10.1088/0004-637x/743/2/156.

M.E. Schwamb et al. Tuning the Legacy Survey of Space and Time (LSST) Observing Strategy for Solar System Science. The Astrophysical Journal Supplement Series, 266(2):22, May 2023. doi: 10.3847/1538-4365/acc173.

N.L. Chabot et al. Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission. The Planetary Science Journal, 5(2):49, February 2024. doi: 10.3847/PSJ/ad16e6.

S.R. Chesley et al. Orbit and bulk density of the OSIRIS-REx target Asteroid (101955) Bennu. Icarus, 235:5–22, June 2014. doi: 10.1016/j.icarus.2014.02.020.

P.W. Chodas. Orbit uncertainties, keyholes, and collision probabilities. In Bulletin of the American Astronomical Society, volume 31, page 1117, January 1999. URL https://ui.adsabs.harvard.edu/abs/1999BAAS...31R1117C.

S.R. Chesley and D. Farnocchia. Guided asteroid deflection by kinetic impact: Mapping keyholes to an asteroid’s surface. In Asteroids, Comets, Meteors 2014, page 92, July 2014. URL https://ui.adsabs.harvard.edu/abs/2014acm..conf...92C.

S. Eggl, S.R. Chesley, P.W. Chodas, and D. Farnocchia. Avoiding Armageddon: Long-Term Asteroid Orbit Deflection Optimization. In 42nd COSPAR Scientific Assembly, volume 42, pages S.3–13–18, July 2018. URL https://ui.adsabs.harvard.edu/abs/2018cosp...42E.957E.

R. Makadia, S.R. Chesley, et al. First detection of an asteroid’s heliocentric deflection: The Didymos system after DART. Submitted, 2025.

How to cite: Makadia, R., Chesley, S., Farnocchia, D., and Eggl, S.: Keyhole-Based Site Selection for Kinetic Impact Deflection of Near-Earth Asteroids, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-77, https://doi.org/10.5194/epsc-dps2025-77, 2025.

Introduction: Developing a suite of models that can address different physical scenarios in the encounter of asteroids is a timely question for planetary defense science. The role of plasma events in dust dynamics in the close vicinity of the asteroid has not been tackled methodologically. After the successful launch of the ESA/HERA mission [1] on October 7, 2024, it is timely to recall what we have learned from the NASA Double Asteroid Redirection Test (DART) impact [2] and the ASI/Light Italian Cubesat for Imaging of Asteroids (LICIACube) [3] mission. Among the scientific objectives of the HERA mission is to determine the physical properties of Dimorphos, including its internal structure, and to constrain binary formation scenarios. Here we present how dust dynamics simulations can help constrain the physical properties of the dust in the asteroid and/or in the binary system, together with a plasma model which can accelerate particles and change their dynamics in the encounter with the asteroid. Such a scenario could be of interest to study the environment of an asteroid that can be subject to strong plasma events, as in the planned ESA/JAXA RAMSES mission to Apophis in 2029.

The models: We couple two models - the 3D+t model – LIMARDE [4] and the MHD model that analyzes shock dynamics and space weather event observations MIM[5]. Dust dynamical simulations are constrained with laboratory observations [6], impact simulations, and near-field observations such as the LICIACube [7] images, and simulate the long-lived ejecta. The model computes single particle trajectories, dust rotational frequencies and velocity, as well as particle orientation at any time and distance. We compute the dust velocity distribution based on the physical properties (size, mass, and shape) derived from the LICIACube observations. The results are useful to check the role of particle fragmentation and to constrain the physical properties based on the dynamical properties of the ejected dust in the near- and mid-environment.

The MIM model studies the MHD instabilities in space weather events and the velocity changes in the plasma flow that can contribute to changes in the dynamics of particles in the vicinity of the asteroid.

Results: The first group of results regards the dust dynamics modeling that will be coupled with the plasma model. We carried out a numerical analysis to determine how many and which non-spherical particles remain gravitationally bound to the Didymos system, how much mass escapes, and the corresponding percentages relative to the total (see Figure 1).

Figure 1. Logarithmic-scale plot showing the relationship between particle velocity and size. This graph refers specifically to the 120th second of the simulation in the presence of a vapor plume, without fragmentation, and includes data for 1000 oblate particles (red squares), 1000 prolate particles (blue diamonds), and 1000 spherical particles (green circles).

References: [1] Michel, P. et al. 2022 PSJ 160 [2] Rivkin, A.S. et al. 2021, PSJ, 2, 24pp; [3] Dotto, E. et al. 2021, PSS 199,  [4] Fahnestock et al. 2022, PSJ; [5] Biasiotti et al. 2024 [6] Ormo et al. 2022, E&PSL [7] Dotto et al. 2024, Nature

How to cite: Ivanovski, S. L., Calderone, L., and Biasiotti, L.: Dust dynamics and plasma simulations in support of planetary defense missions such as HERA and RAMSES, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1841, https://doi.org/10.5194/epsc-dps2025-1841, 2025.

The AIDA planetary defense program, consisting of the U.S. DART and Europe’s Hera missions, is currently underway. In September 2022, the DART spacecraft successfully conducted an impact experiment on Dimorphos, the satellite of the binary asteroid Didymos (Daly et al., 2023). The Hera mission is scheduled to arrive at Didymos–Dimorphos in December 2026 and will closely observe the artificial crater created by DART. Japan's thermal infrared camera (TIRI), installed on the Hera spacecraft, aims to reveal the thermal properties of the asteroid surface, such as thermal inertia, porosity, and surface roughness.

The evolution of an asteroid's orbits and rotation is affected by gravitational forces from the Sun and planets and by non-gravitational forces due to thermal radiation pressure. We aim to construct theoretical and numerical models of non-gravitational effects acting on binary asteroids and validate them with the Hera mission.

The orbital evolution of a binary asteroid’s satellite is mainly driven by tidal forces and the binary YORP (BYORP) effect. In many binary systems, the primary spins relatively fast, and the satellite’s semi-major axis increases due to tidal evolution. On the other hand, the BYORP effect is a torque generated by the thermal radiation of a synchronously rotating satellite, which can alter the semi-major axis depending on the irregularity of the satellite’s shape (Ćuk & Burns, 2005).

In this study, we newly focused on the Yarkovsky effect acting on the satellite of a binary asteroid. In particular, we analyzed the Yarkovsky-Schach effect, a mechanism that has been studied in the orbital evolution of Saturn’s ring particles and is considered to similarly affect satellites in binary asteroid systems (Rubincam, 2006; Vokrouhlický et al., 2007). We developed both analytical and numerical models of the Yarkovsky-Schach effect acting on a binary asteroid satellite (Zhou, Vokrouhlický, Kanamaru, et al., 2024).

For numerical simulations of the non-gravitational forces acting on the satellite, we used the thermophysical computation library AsteroidThermoPhysicalModels.jl, which is also applicable to binary systems. The results show that satellites experiencing frequent eclipses (in the case of prograde rotation) tend to evolve toward tidally locked orbits due to the Yarkovsky-Schach effect. This orbital evolution mechanism offers essential insights into the statistical properties and the dynamical lifetimes of binary asteroids.

How to cite: Kanamaru, M. and Zhou, W.: Non-Gravitational Effects on a Binary Asteroid: Implications for the Long-term Dynamics of Asteroid Didymos-Dimorphos, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-609, https://doi.org/10.5194/epsc-dps2025-609, 2025.

How to cite: Föhring, D., Dölling, E., Cordelli, E., Klug, J., Messing, R., Conversi, L., Ramirez Moreta, P., Micheli, M., Ocana, F., Kresken, R., and Devogele, M.: Commissioning and First Light Results of ESA’s Flyeye-1 Telescope , EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1017, https://doi.org/10.5194/epsc-dps2025-1017, 2025.

To warn about potential asteroid or comet impacts, we must first observe and discover these objects through dedicated NEO surveys. Most current and planned surveys are ground-based and use visible light, but they face limitations like weather dependency, limited sky visibility, difficulty detecting at low galactic latitudes, and inability to determine physical properties directly. A space-based mission at the Sun-Earth Lagrange point (L1) using thermal infrared could address these issues by scanning areas of the sky inaccessible from the ground and providing early warnings of imminent impacts.

To fill the abovementioned gap, ESA is studying an NEO Mission in the Infra-Red, called NEOMIR hereafter. NEOMIR aims to detect objects of at least 35 m in diameter (i.e., similar to the Tunguska event) from within Earth's orbit with enough lead time for mitigation. It does this by pointing at relatively low solar elongation, i.e., in directions angularly close to the Sun at all Ecliptic latitudes, shortening exposure times, and increasing revisit cadence to avoid missing faster NEOs. The infrared data will help determine initial orbits and sizes.

We will present the mission and spacecraft design, the status of the project, as well as initial results on expected detection capabilities. We will focus on the NEOMIR ability to detect possible Earth impactors and todetermine their orbits and impact locations. We will also analyse what would have been the NEOMIR contributions in real-case scenarios such as the Chelyabinsk impactor and 2024 YR4.

How to cite: Conversi, L., Licandro, J., Delbo, M., Mueller, T., Muinonen, K., Popescu, M., and Tanga, P.: NEOMIR: project statut of ESA’s space-based infrared mission for NEO detection and early warning, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1329, https://doi.org/10.5194/epsc-dps2025-1329, 2025.

NASA’s Near-Earth Object (NEO) Surveyor mission is an infrared observatory planned to launch no earlier than September 2027 that is designed to discover and characterize asteroids and comets. Its main objective is to identify those objects that are large enough (>140 m in effective spherical diameter) to cause severe regional damage from impact. The observatory will operate at the Sun-Earth L1 Lagrange point and conduct a survey to within 45° of the Sun in order to identify objects in the most Earth-like orbits[1]. During the length of the survey, NEO Surveyor is estimated to discover ~200,000 to 300,000 new objects (some as small as ~10 m) and thousands of comets. These discoveries will provide a more comprehensive understanding of the orbital and size frequency distribution of the NEO population, and also provide insights into the relative probability of an Earth impact during the next 100 years.

NEO Surveyor’s ability to observe regions close to the Sun increases the likelihood that it will detect objects in very Earth-like orbits. These objects tend to have the lowest minimum orbit intersection distances (MOIDs), and thus pose the greatest risk of Earth impact. NEOs on more Earth-like orbits are also more difficult to deflect, all else being equal. This attribute of NEO Surveyor’s operation is not only important for planetary defense considerations, but it also provides an opportunity to identify low-delta V spacecraft mission targets, which are of interest to the science, in situ resource utilization, and exploration communities.

The NEO Surveyor team has developed a model reference population of NEOs and other Solar System objects (e.g., mainbelt asteroids) in which to measure the effectiveness of the survey over its designed operational lifetime. This Reference Small Body Population Model (RSBPM) combines both a separate NEO model and a background object model to mimic the moving objects that the observatory will “see” during the operation of the survey. Based on the RSBPM, NEO Surveyor will be able to identify objects that are particularly accessible for both one way and round-trip rendezvous missions and span a range of NEO diameters. The majority of these low-delta V objects will likely be Atens, but will also include a significant number of Apollos.

In this paper, we will apply astrodynamics techniques to estimate the distribution of delta V and flight time requirements for both one-way and round-trip rendezvous missions to the population of NEOs that NEO Surveyor is expected to discover. We will utilize the algorithms for the Near-Earth Object Human Space Flight Accessible Targets Study (NHATS)[1] [2], heuristics derived from the current NHATS data, and other techniques specific to one-way rendezvous trajectory calculations. The results will show us how the number of known attractive NEO mission targets may increase during NEO Surveyor’s survey operations.

References

[1]  Mainzer, A. K., J. R. Masiero, P. A. Abell, J. M. Bauer, W. Bottke, B. J. Buratti, S. J. Carey, D. Cotto-Figueroa, R. M. Cutri, D. Dahlen, P. R. M. Eisenhardt, Y. R. Fernandez, R. Furfaro, T. Grav, T. L. Hoffman, M. S. Kelley, Y. Kim, J. D. Kirkpatrick, C. R. Lawler, E. Lilly, X. Liu, F. Marocco, K. A. Marsh, F. J. Masci, C. W. McMurtry, M. Pourrahmani, L. Reinhart, M. E. Ressler, A. Satpathy, C. A. Schambeau, S. Sonnett, T. B. Spahr, J. A. Surace, M. Vaquero, E. L. Wright, G. R. Zengilowski, and the NEO Surveyor Mission Team. “The Near-Earth Object Surveyor Mission”, The Planetary Science Journal, 4:224 (19pp), 2023 December.

[2] Barbee, B. W., Abell, P. A., Adamo, D. R., Alberding, C. M., Mazanek, D. D., Johnson, L. N., Yeomans, D. K., Chodas, P. W., Chamberlin, A. B., Friedensen, V. P., "The Near-Earth Object Human Space Flight Accessible Targets Study: An Ongoing Effort to Identify Near-Earth Asteroid Destinations for Human Explorers," 2013 IAA Planetary Defense Conference, Flagstaff, AZ, April 15-19, 2013

How to cite: Abell, P., Spahr, T., Barbee, B., Dahlen, D., Mainzer, A., and Masiero, J.: Predicted Discovery of Low-Delta V Targets Among the NEO Population by NEO Surveyor, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-460, https://doi.org/10.5194/epsc-dps2025-460, 2025.

An impact by an asteroid or comet onto the Earth is one of the few natural disasters that can be predicted in advance and that we have the tools to prevent. Without sufficient follow-up observations during their discovery apparitions, NEOs often accrue large uncertainties in position during typical intervals between apparitions. Some NEOs can become effectively “lost” when their positional uncertainties are large enough such that they are more likely to be rediscovered by chance than to be recovered by observations targeted to their ephemerides (Milani 1999). SPACEWATCH®, which pioneered using CCDs to survey the sky for NEOs, currently conducts Near Earth Object (NEO) follow-up observations. To improve planetary defense capabilities by reducing the uncertainty in NEO orbital elements, we conduct full-time rapid astrometric follow-up observations of high priority NEOs as the sole users of the Lunar and Planetary Laboratory’s Spacewatch 1.8-m observatory and the Steward Observatory’s 0.9-m telescope on Kitt Peak. Additionally, we conduct astrometric follow-up with Steward Observatory’s Bok 2.3-m telescope during bright time with the Spacewatch Cassegrain Camera (SCC) (see Table 1).

Our highest priority targets for NEO astrometric follow-up are virtual impactors (VIs) and Potentially Hazardous Asteroids (PHAs). PHAs are ≳140 meters in diameter with Earth Minimum Orbit Intersection Distances (EMOIDs) ≲ 0.05 au. VIs have sufficiently uncertain heliocentric orbital parameters such that at least one orbit solution predicts an Earth impact within 100 years. PHAs pose a greater hazard due to their size, but the majority do not have orbits in which the asteroid could impact Earth itself. VIs pose a greater impact risk due to their real (but low) probability of impact. Currently, only ~1% of NEAs on the JPL Sentry risk list of VIs are “large” (>140 m). It is particularly important to minimize the orbit uncertainties for VI PHAs to rule out (or in) possible impacts.

Spacewatch has observed a majority of the newly discovered NEOs that are or were on JPL’s VI impact risk list since October 16, 2019. According to the PDS SBN, from Sept. 1993 through March 2025, the 1.8-m is third in making the first observation for follow-up MPECs, sixth in follow-up MPECS, and fifth over all types of MPECs. It is fifth in MPECs for making the first follow-up observation over the past year. The 0.9-m is sixth in discovery MPECs and eighth in precovery MPECs from September 1993 through March 2025.  SPACEWATCH® also leads in faint observations (V>22.0) as shown in Figure 1.

In addition to our regular follow-up observations, SPACEWATCH® has a Target-of-Opportunity program for recovery of potential impactors. This includes applying for open time at larger telescopes (4 to 8m class), such as the LBT, the MMT, Gemini North and South, CTIO Blanco, Keck, and SOAR. The observations are triggered when a Virtual Impactor becomes too faint to follow up with smaller class telescopes, is large enough to be dangerous, and still has a high impact probability and/or high Palermo Scale value. ToO measurements of VI 2022 LX illustrate the benefit of using a large telescope to recover a VI. It was discovered on 2022 May 22 and observations were collected by smaller telescopes through July 5 while it was V < 23. We triggered a ToO with LRIS on Keck I on 2022 July 28 to extend the timespan of its observations by 23 nights. After we submitted our astrometry to the Minor Planet Center (MPC), the orbital recalculation led to a decrease in the orbital element uncertainties by ~30% (Table 2) and ruled out the potential impacts.

In 2019, SPACEWATCH®, Catalina Sky Survey (CSS) and the University of Minnesota began the Bok NEO Survey, a collaborative survey program using 90Prime on the Bok 2.3-m Telescope to discover faint asteroids, especially larger NEOs and Earth Trojan candidates. New discoveries include the imminent impactor 2024 XA1 which broke up in the atmosphere over Siberia, the hyperbolic Comet C/2025 D1 (Gröller) and Apollo NEA 2025 EW3 which has a diameter of 860m (possibly larger). From the start of the Bok NEO survey on November 15, 2019 through April 10, 2025, the observatory was operational for 48.5 months over which we averaged an allocation of 7.2 nights per month of dark/grey time from Steward Observatory. NASA’s Planetary Data System’s Small Bodies Node’s MPEC Watch reports that of the top MPEC’d discoverers, this survey is fourth over the past 5 year and is sixth since September 19, 1993. Of the top MPEC’d precoverers, it is eighth over the past year and ninth over the past 5 years (https://sbnmpc.astro.umd.edu/mpecwatch/index.html).

How to cite: Lejoly, C., Brucker, M., McMillan, R. S., Bressi, T., Larsen, J., Mastaler, R., Read, M., Scotti, J., and Tubbiolo, A.: SPACEWATCH®: Following up Near-Earth Objects (NEOs) to help Determine their Orbits, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-481, https://doi.org/10.5194/epsc-dps2025-481, 2025.

One of the major achievements of planetary science in the past century has been the discovery of a population of asteroids and comets that have the potential to impact our planet. These objects are collectively known as Near-Earth Objects (NEOs), which include both asteroids and comets whose orbits bring them within 1.3 astronomical units (au) of the Sun. Among them, a subset is classified as Potentially Hazardous Asteroids (PHAs) — objects that have an Earth Minimum Orbit Intersection Distance (MOID) of 0.05 au or less and an absolute magnitude (H) of 22 or brighter, indicating a size large enough to cause significant damage in the event of an impact. Imminent Earth impactors have been shown to "come" from two principal directions in the sky, one towards local midnight and the other towards the local midday [1].

While midnight impactors are well covered by existing optical survey telescopes, midday impactors present a major observational challenge. From the ground, observations in the direction of the Sun are nearly impossible due to its overwhelming brightness, which prevents the detection of faint asteroid signals. The Chelyabinsk event of 2013 highlighted this vulnerability, as the ~20-meter asteroid responsible for the airburst was completely undetected before impact, approaching from a region of the sky that was effectively unobservable by existing surveys [2]. A promising solution to this problem is to place an infrared telescope at the Sun-Earth L1 Lagrange point. From this vantage point, such an observatory would be able to scan the region of space closest to the Sun with unprecedented sensitivity, detecting asteroids that would otherwise remain hidden. This is the fundamental concept behind NEOMIR (Near-Earth Object Mission in the Infrared), a proposed ESA concept mission, designed to provide early warning for asteroids approaching from the daytime sky [3]. NASA's Near-Earth Object (NEO) Surveyor will also be at L1 Lagrange point [4], but NEOMIR will be complementary in terms of survey region. By observing in the infrared at small solar elongations, NEOMIR would complement existing ground-based surveys and significantly enhance our ability to detect and respond to imminent impact threats. By positioning NEOMIR at the Sun-Earth Lagrange point L1, ESA aims to maximize early detection capabilities for hazardous asteroids approaching from the Sun’s direction. However, these asteroids are typically detected at high phase angles (angle between the Sun and the observer as seen from the asteroid) as seen from NEOMIR at L1 Lagrange point.

Hence, the mission’s success will depend on addressing the technical and observational challenges posed by high phase-angle detections, ultimately improving our ability to provide timely warnings for potential impactors. Unlike visible-light observations, which rely on sunlight reflected off an asteroid’s surface, in the medium infrared it is possible to measure the thermal radiation emitted by the asteroid itself. This advantage becomes especially crucial at high phase angles — when the Sun, the asteroid, and the observer form a nearly straight line. At such angles, only a small fraction of the asteroid’s illuminated surface is visible in reflected light, making it difficult to detect the body. However, in the thermal infrared, an asteroid's emission originates from most of its surface, which remains warm and radiates detectable heat. Despite these advantages, observing asteroids in the thermal infrared at high phase angles presents significant challenges. The extreme observing geometry complicates flux predictions, as both standard and sophisticated thermal models have not been fully validated for such conditions. Additionally, space-based detectors operating near the Sun must contend with high background noise from zodiacal dust emission and stray light, which can limit sensitivity. Overcoming these obstacles requires careful optimization of telescope location, observation strategy, and data processing techniques.

To simulate NEOMIR observations of imminent Earth impactors, we employ a ThermoPhysical Model (TPM; implementation based on [5]) to compute infrared fluxes from synthetic asteroid populations. These fluxes will then be analyzed with simple thermal models, which output the estimated diameter of the synthetic asteroid. The error between these derived diameters and the original ones (used as input for the TPM) will then be discussed. In this presentation, we provide an overview of the NEOMIR mission and present a simulation framework to estimate the infrared fluxes of synthetic asteroids, using a TPM and physically plausible assumptions about their properties (e.g., thermal inertia and pole orientations).

Acknowledgments
This work was supported by the French government through the France 2030 investment plan managed by the National Research Agency (ANR), as part of the Initiative of Excellence Université Côte d’Azur under reference number ANR-15-IDEX-01. This work was supported by JSPS KAKENHI grant Number JP23KJ0640.

References:
[1] Veres et al., 2009, Icarus, Vol. 203, 472.
[2] Müller et al., submitted to Advances in Astronomy.
[3] Conversi et al., 2024, Proceedings of the SPIE, Vol. 13092, 130922H.
[4] Mainzer et al., 2023, PSJ, Vol. 4, 224.
[5] Delbo’ et al., 2007, Icarus, Vol. 190, 236.

How to cite: Beniyama, J., Delbo, M., Müller, T., Conversi, L., Maria Revellino, M., Tanga, P., Muinonen, K., and Licandro, J.: On the detection and characterization of potential Earth-impacting asteroids from space in the thermal infrared, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1497, https://doi.org/10.5194/epsc-dps2025-1497, 2025.

The Mission Accessible Near-Earth Object Survey (MANOS) conducts characterization observations of objects on low delta-v orbits and in the sub-km size regime where knowledge of physical properties is sparse. Spectroscopic characterization of these objects serves to constrain the distribution of taxonomic and compositional types across the population of the most frequent Earth-impacting asteroids, including the direct precursors of meteorites. Such data can probe how spectral properties may be dependent on factors such as object size (Devogele et al. 2019), Earth encounter distance (Binzel et al. 2010), and/or perihelion distance as a proxy for peak surface temperature (Graves et al. 2019). Constraints on the ensemble spectral properties of potential Earth impactors, as well as improved understanding of how those properties evolve over time, has implications for assessing the planetary defense risk associated with the NEO population.

We will present the results of MANOS spectrophotometric observations for a sample of 199 NEOs (Figures 1 and 2). Observations were performed between 2014 and 2025 from the 4.3-m Lowell Discovery Telescope (LDT), the 4.1-m Southern Astrophysical Research Telescope (SOAR), and the 4-m Mayall Telescope. At all facilities we collected images using the SDSS griz filter set with respective band centers at 0.48, 0.62, 0.76 and 0.91 microns. These multi-band data were used to derive colors and to assign a spectral taxonomic type to each object based on a down-sampling of taxonomic templates from the Bus-DeMeo system (DeMeo et al. 2009). Observing strategies were employed to constrain the lightcurves of targets, which proved necessary to properly account for rotational brightness variations during the collection of non-simultaneous images in each filter. For example, we either measured a full rotational lightcurve before collecting a color sequence, or we interleaved images in a single reference filter to track and correct for lightcurve variations (e.g. a filter sequence of seven exposures in order r-g-r-i-r-z-r). Our sample of colors accessed objects as faint as r~22, which is about 1-2 magnitudes fainter than is typically observable with spectroscopic techniques. However, the reduction of spectral information down to just four channels can limit the ability to achieve unique spectral taxonomic classifications and is not well suited to detailed compositional analysis.

This work highlights several key findings. First, the distribution of taxonomic types from the color data is consistent with previously published MANOS spectroscopic results (Devogele et al. 2019). However, this distribution is distinct from analogous surveys that sample the larger end of the NEO size distribution (H<22). In particular we find a deficit of S-type asteroids and an overabundance of X-complex asteroids amongst sub-km NEOs. It remains unclear the extent to which this is a size-dependent compositional trend in the NEO population, a size-dependence on physical surface properties such as regolith grain size, and/or a consequence of various observational biases that can be more pronounced for small (H>20) objects.

Our second major finding is related to the influence of lightcurve variations on derived colors. Our approach of non-simultaneous multi-filter imaging found that ~75% of the sample required treatment of lightcurve variability to derive reliable colors. Not accounting for this variability would produce significantly different results, where some objects would appear as part of an entirely different taxonomic complex. This would clearly have consequences for interpretation of individual objects, but also manifests as a systematic bias in the distribution of spectral types based on colors derived from non-lightcurve corrected data. Specifically, we see an over-abundance of C-complex spectral types when lightcurve variability is not treated: with lightcurve correction we find 10±5% (1-sigma) of the sample is classified as C-type, without lightcurve correction this fraction increases to 27±7%. Finding a reason for this over-abundance is an area of ongoing work. However, it is clear that lightcurve variability must be considered in any color survey that involves non-simultaneous observations across multiple filters. Of course this issue is eliminated for instruments that can obtain simultaneous multi-band images.

Finally, we identified a number of unusual objects in our sample. This includes objects observed on multiple epochs that demonstrated significantly different colors across epochs. For example, the colors 2011 CG2 were best fit by a Cgh-type on one epoch and a Q-type on a second epoch. Such variability is highly unexpected and is not well understood. We also note the unusual colors of 2022 BX5, which appears as the isolated object in the upper right of Figure 2. These are the reddest colors measured for any NEO to date and are most consistent with D-type spectra that are more common in the outer Solar System.

This work acknowledges funding support from NASA grants 80NSSC21K1328, NNX17AH06G, and NNX14AN82G.

References:

Binzel et al. (2010), Nature 463, 331.

Binzel et al. (2019) Icarus 324, 41.

Birlan et al. (2024) A&A 689, A334.

DeMeo et al. (2009) Icarus 202, 160.

Devogele et al. (2019), AJ 158:196.

Graves et al. (2019), Icarus 322, 1.

Ivezic et al. (2019) AJ 122, 2749.

Navarro-Meza et al. (2024) AJ 167:163.

Perna et al. (2018) Planetary and Space Science 157, 82.

Sanchez et al. (2024) PSJ 5:131.

Figure 1: Cumulative size frequency distributions of key NEO spectral surveys. The number of objects sampled by each survey are given in parentheses in the legend. MANOS generally focuses on sub-km objects (H>20). The sample for our spectrophotometric survey is shown as the bold red curve. References for each survey: MITHNEOS (Binzel et al. 2019), NEOROCKS (Birlan et al. 2024), NEOSHIELD2 (Perna et al. 2018), RATIR (Navarro-Meza et al. 2024), Sanchez et al. (2024), and MANOS spectra (Devogele et al. 2019).

Figure 2: g-i versus i-z color-color plot for the 199 objects observed in the MANOS spectrophotometric survey. The taxonomic assignment for each object is indicated by the plotted letters. Data from LDT are in black, from SOAR in red, and from Mayall in yellow. The blue density contours in the background represent the colors of 223 NEOs from the Sloan Digital Sky Survey Moving Object Catalog (Ivezic et al. 2001).

How to cite: Moskovitz, N., Hemmelgarn, S., Zigo, H., Kareta, T., Devogele, M., and Thirouin, A.: NEO Colors from The Mission Accessible Near-Earth Object Survey (MANOS), EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1338, https://doi.org/10.5194/epsc-dps2025-1338, 2025.

The Near-Earth Object Surveyor (NEO Surveyor; Mainzer et al., 2023) is a NASA mission designed to advance planetary defense by discovering near-Earth asteroids. Operating from a halo orbit at the Sun-Earth L1 Lagrange point, NEO Surveyor will conduct a wide-field, mid-infrared survey with an emphasis on detecting potentially hazardous asteroids (PHAs) — objects larger than 140m with minimum orbital intersection distances (MOIDs) with Earth of less than 0.05au. NEO Surveyor’s mid-infrared bandpasses will directly measure asteroids’ thermal emission, providing a strong constraint on size which is necessary for hazard assessment. 

In this work, we analyze the expected fitted-orbit quality and time-evolution of the corresponding on-sky ephemeris uncertainties for newly-discovered PHAs and smaller asteroids from NEO Surveyor. This assessment is important for the mission itself and for understanding the ground-based follow-up regime that NEO Surveyor will create.

To discover previously unknown near-Earth asteroids, NEO Surveyor’s images will be processed through the NEO Surveyor Survey Data System (NSDS). The NSDS will construct difference-images that will be processed by the Moving Object Detection Pipeline (MODP) to identify “tracklets” from Solar system objects — groups of four or more detections within several hours of each other. These tracklets will be submitted to the Minor Planet Center (MPC) within three days of detection, which will associate the tracklet with a known object, link the tracklet to previously-submitted tracklets, or retain the “isolated” tracklet for possible future linking. Previously unknown objects will require at least two linked NEO Surveyor tracklets to be cataloged as a new discovery. Previously known objects (not the focus of this study) will benefit from linkage to archival observations, yielding longer arcs and well-constrained orbits.

We simulate NEO Surveyor’s discoveries using the NEO Surveyor Survey Simulator (NSS; Masiero et al., 2023), an injection-and-recovery framework that compares the expected flux of simulated objects to the observatory’s projected sensitivity at that point on the sky. Our simulations begin with a reference population of near-Earth asteroids, to which we apply the NEO Surveyor Known Object Model (Grav et al., 2023). This method tags each object as “known” or “unknown” at the beginning of the mission, allowing us to specifically estimate the orbit quality of new objects despite using an injected population of only synthetic asteroids.

After constructing tracklets with NSS, we process those tracklets in find_orb (Gray, 2022) for initial orbit determination. To assess orbit quality, we examine formal uncertainties in orbital elements, the MPC’s orbital uncertainty “U” parameter, and projected ephemeris uncertainties at future epochs. For planetary defense applications, we also focus on the precision in MOID determination — this metric provides a key assessment of impact risk. We validate our methodology by running known objects through the survey simulation and orbit-fitting pipeline, then comparing the orbital solutions and ephemeris predictions with JPL Horizons.

NEO Surveyor’s observational strategy has typical revisit times on the order of two weeks, meaning that a two-tracklet observational arc spans at least this time; this attribute of the cadence places the discovery tracklets in a fundamentally different regime than contemporary ground-based surveys that usually construct shorter discovery arcs. NEO Surveyor will observe across a range of Solar elongations (as low as ~45 degrees), including areas challenging or impossible for ground-based telescopes to observe. Thus, ground-based follow-up will often need to wait until NEO Surveyor discoveries reach an observable Solar elongation (if ever). For objects that do eventually become observable from Earth, understanding the evolution of on-sky uncertainties after NEO Surveyor’s discovery is paramount.

We analyze the expected orbit quality from NEO Surveyor across orbital classes (Apollos, Amors, Atens, and Atiras) and physical sizes. Specifically, we correlate arc length and other detection statistics with orbit uncertainties from find_orb. Most PHAs and a large fraction of smaller objects achieve discovery arcs beyond the minimum two-tracklet track. The median track for an observed PHA apparition contains four tracklets; find_orb returns excellent orbital solutions for nearly all these median cases and for many shorter arcs. For objects with the shortest allowable discovery track — the most challenging orbit-fitting scenario with two minimally-spaced tracklets — we characterize how on-sky uncertainties change over time to inform ground-based follow-up. Many PHAs with two-tracklet arcs, even those that aren’t immediately ground-observable, should be recoverable with modern follow-up systems.

Finally, we project the evolution of orbit quality at the catalog-level throughout the mission, showing the expected state after each year of operations. NEO Surveyor’s cadence will naturally follow-up many of its own discoveries during operations and produce high-quality orbits. For those objects, ground-based data in visible wavelengths can produce complementary measurements of albedo, color, rotation rates, and lightcurve amplitudes. In summary, our analysis helps maximize NEO Surveyor’s contributions to planetary defense and planetary science by ensuring that new discoveries can be effectively monitored and characterized.

How to cite: Levine, W. G., Linder, T., Spahr, T., Masiero, J., Chesley, S., Mainzer, A., and NEO Surveyor Team, T.: Orbit Quality Projections for New Discoveries by the Near-Earth Object Surveyor, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1143, https://doi.org/10.5194/epsc-dps2025-1143, 2025.

Introduction

Near-Earth asteroids (NEAs) are asteroids with perihelion distances < 1.3 AU, whose orbits bring them close to Earth (Kokhirova and Babadzhanov 2023). They provide a unique sample of Solar System material, often transported to the inner regions after millions of years of gravitational interactions with the planets. 

Binary asteroids or binaries are systems composed of at least two bodies gravitationally bound together (Margot 2015). A substantial fraction of NEAs is found in binary systems: approximately 15% of NEAs larger than 200 m in diameter host a satellite (Pravec et al. 2006; Margot et al. 2002). Given that approximately 11,000 NEAs with these characteristics are currently known, it is estimated that around 1,600 of them could be binary systems. Recent discoveries related to the population of binary asteroids continue to increase. 

Context

Binary systems can form through various mechanisms: collisions, tidal effects during close planetary encounters, spin-up and subsequent fission due to the YORP effect, or rotational instability (Margot 2015). Each asteroid presents unique physical characteristics, differing in size, shape, chemical composition, density, and surface structure (DeMeo et al. 2009). Taxonomic classification and the mineralogical study of asteroids are essential tools for understanding the heterogeneity of these bodies and tracing their evolutionary history.

Their short distance to the Earth gives more easy access to the study of their different physical and compositional characteristics, and formation mechanisms. These properties are way more difficult to determine in furthest main-belt asteroids. This may deepen our understanding of collisional processes and gravitational interactions and estimate mass and density (Merline et al. 2002 , Margot 2015). These properties, along with the taxonomic classification and mineralogical characterization, increase our knowledge of the asteroid population in the Solar System. 

Beyond their scientific value, binary asteroids have become important in the context of planetary defense, as demonstrated by the Didymos binary system. This system is the primary target of the international collaboration AIDA (Asteroid Impact and Deflection Assessment, Cheng 2015), which includes NASA's DART mission (Double Asteroid Redirection Test; Rivkin et al. 2021) and ESA's Hera mission (Michel et al. 2022).

Aim

This work presents the preliminary spectroscopic analysis and taxonomic classification of eight binary NEAs: (137170) 1999 HF1, (539940) 2017 HW1, (85804) 1998 WQ5, (420302) 2011 XZ1, (35107) 1991 VH, (385186) 1994 AW1, (175706) 1996 FG3, and (65803) Didymos.

In this list of targets, three very well known objects appear. Didymos, the asteroid impacted by NASA's DART mission, will be further studied by ESA's Hera mission, which is scheduled to investigate the binary system in early 2027. In addition to Didymos, other relevant targets such as 1991 VH and 1996 FG3 are included in this work. These objects exhibit low delta-V values and may be potential candidates for future space missions. 

Methods

Observations were conducted as part of the NEOROCKS (NEO Rapid Observation, Characterization and Key Simulation) project (funded by ESA) using visible spectroscopy with the 1.22 m Galileo Telescope (Unipd) and the 1.82 m Copernico Telescope (INAF-OAPD) at Asiago Observatory. Spectra were obtained through low-resolution spectroscopy in the wavelength range from 4500 to 9500 Å. Data reduction was performed using the Image Reduction and Analysis Facility (IRAF) software.

For each object, normalization was computed at 6000 Å, ensuring that the result is less influenced by noise. The spectral slope was computed, and a chi-square comparison was carried out with reference taxonomic curves from Bus and DeMeo (2009). The best-fitting meteorite analogs were identified using the M4AST tool and the RELAB database (see Fig. 1). Figure 1 shows the spectrum of asteroid 1991 VH in cyan and that of asteroid 2017 HW1 in blue, as an example. The two dashed curves correspond to the Cb taxonomic curve, with the associated meteorite analog being a C1 Carbonaceous Chondrite (shown in purple).

Results

Preliminary results reveal taxonomic diversity among the studied asteroids: two are classified as Cb-type (1999 HF1, 2017 HW1, associated with C1 Carbonaceous Chondrites), one as O-type (1998 WQ5, associated with Anomalous Ureilite Achondrite), one as Cg-type (2011 XZ1, associated with CM Unusual Carbonaceous Chondrite), one as Sq-type (1991 VH), one as Q-type (1994 AW1), one as Cb-type (1996 FG3, associated with C1 Carbonaceous Chondrite), and one as S-type (Didymos, associated with Ordinary Chondrite).

Conclusions

With this work we will present the preliminary results of the taxonomic and mineralogical classification of eight binaries. This characterization increases the information on the chemical composition of these objects. By improving our understanding of their physical and compositional properties, this study offers some insight into the characteristics of near-Earth asteroids, which may support future research on these binary objects.

References:

• G. I. Kokhirova and P. B. Babadzhanov, Current Knowledge of Objects Approaching the Earth, Solar System Research 57, 467 (2023).
• P. Pravec et al., Photometric survey of binary near-Earth asteroids, Icarus 181, 63 (2006).
• J. L. Margot et al., Binary Asteroids in the Near-Earth Object Population. Science 296, 1445-1448 (2002)
• J. L. Margot et al., Asteroid Systems: Binaries, Triples, and Pairs, Asteroids IV (2015).
• W. J. Merline, Asteroids Do Have Satellites, Asteroids III, W. F. Bottke Jr., A. Cellino, P. Paolicchi, and R. P. Binzel (eds), University of Arizona Press, Tucson, p.289-312 (2002).
• A. Cheng and P. Michel, Asteroid Impact and Deflection Assessment mission: the Double Asteroid Redirection Test (DART), European Planetary Science Congress 2015.
• A. S. Rivkin, The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements, the Planetary Science Journal, Volume 2, Issue 5, id.173, 24 pp. (2021).
• M. Patrick, The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos, The Planetary Science Journal, Volume 3, Issue 7, id.160, 21 pp. (2022).
• F. E. DeMeo, An extension of the Bus asteroid taxonomy into the near-infrared, Icarus, Volume 202, Issue 1, p. 160-180 (2009).

Figure 1 Spectra of asteroid 1991 VH (cyan) and asteroid 2017 HW1 (blue). The two dashed curves correspond to the Cb taxonomic curve, with the associated meteorite analog being a C1 Carbonaceous Chondrite (purple).

How to cite: Farina, A., Lazzarin, M., La Forgia, F., Mura, A., Frattin, E., and Ochner, P.: Visible Spectroscopic Characterization of Eight Binary Near-Earth Asteroids, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1300, https://doi.org/10.5194/epsc-dps2025-1300, 2025.